U.S. patent number 7,166,195 [Application Number 10/619,393] was granted by the patent office on 2007-01-23 for grooved and perforated layer for use in papermakers' fabric.
This patent grant is currently assigned to Albany International Corp.. Invention is credited to John Hawes.
United States Patent |
7,166,195 |
Hawes |
January 23, 2007 |
Grooved and perforated layer for use in papermakers' fabric
Abstract
A grooved perforated layer for use in a papermakers' fabric is
provided. The grooves serve to diffuse flow at the surface of the
perforated layer so as to reduce the pressure drop across the layer
and thereby reduce the migration of fines. In this manner, the
light/dark pattern associated with the fines is avoided and the
quality of the resulting paper sheet is improved.
Inventors: |
Hawes; John (Averill Park,
NY) |
Assignee: |
Albany International Corp.
(Albany, NY)
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Family
ID: |
34062571 |
Appl.
No.: |
10/619,393 |
Filed: |
July 15, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050013969 A1 |
Jan 20, 2005 |
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Current U.S.
Class: |
162/358.2;
428/131; 442/270; 442/286; 428/169; 428/167; 428/137; 442/394;
162/900 |
Current CPC
Class: |
D21F
1/0036 (20130101); D21F 7/083 (20130101); Y10S
162/90 (20130101); Y10T 442/674 (20150401); Y10T
428/24273 (20150115); Y10T 442/3724 (20150401); Y10T
428/24587 (20150115); Y10T 428/24322 (20150115); Y10T
428/2457 (20150115); Y10T 442/3854 (20150401) |
Current International
Class: |
D21F
7/08 (20060101); B32B 27/12 (20060101); B32B
5/06 (20060101) |
Field of
Search: |
;162/203-207,306,348,358.1,358.2,358.4,900-904 ;139/383A,425A
;100/37 ;428/131-138,152-154,156,163,167,169
;442/268-270,286,394 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 881 327 |
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Dec 1998 |
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EP |
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891860 |
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Mar 1962 |
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GB |
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1 598 948 |
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Sep 1981 |
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GB |
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WO 91/14558 |
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Oct 1991 |
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WO |
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WO 92/17643 |
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Oct 1992 |
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WO |
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WO 98/01618 |
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Jan 1998 |
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WO |
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WO 98/21403 |
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May 1998 |
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WO |
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WO 98/56982 |
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Dec 1998 |
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WO |
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Primary Examiner: Hug; Eric
Attorney, Agent or Firm: Frommer Lawrence & Haug LLP
Santucci; Ronald R.
Claims
What is claimed is:
1. A layer for use in a papermakers' fabric, comprising: a
plurality of land areas; a plurality of groove areas; a plurality
of perforations extending from a top surface to a bottom surface of
said layer; and wherein the combination of said land areas, groove
areas and perforations minimize pattern formation on said paper
sheet.
2. A layer as claimed in claim 1 wherein said groove areas lie in a
plane.
3. A layer as claimed in claim 1 wherein said land areas lie in a
plane.
4. A layer as claimed in claim 1 wherein said groove areas lie in a
plane and said land areas lie in a plane.
5. A layer as claimed in claim 4 wherein said plane of said groove
areas and said plane of said land areas are parallel.
6. A layer as claimed in claim 1 which includes a series of groove
areas, some of which are positioned at an angle greater than 0
degrees to a machine direction.
7. A layer as claimed in claim 6 wherein said series of groove
areas are in a cross hatched pattern.
8. A layer as claimed in claim 1 wherein said perforations are
dispersed throughout both said land areas and said groove areas,
and wherein one or more of said perforations lies across the
interface of a land area and a groove area.
9. A layer as claimed in claim 1 wherein said perforations are only
in said groove areas.
10. A layer as claimed in claim 1 wherein said perforations are
only in said land areas.
11. A method of forming a layer for use in a papermakers' fabric,
comprising the steps of: forming a plurality of grooves in a base
material so as to form a modified base material having a plurality
of land areas and a plurality of groove areas; and perforating said
modified base material so as to form a plurality of perforations
extending from a top surface to a bottom surface in said modified
base material, wherein the combination of said land areas, groove
areas and perforations minimize pattern formation on said paper
sheet.
12. A method as claimed in claim 11 wherein said groove areas lie
in a plane.
13. A method as claimed in claim 11 wherein said land areas lie in
a plane.
14. A method as claimed in claim 11 wherein said groove areas lie
in a plane and said land areas lie in a plane.
15. A method as claimed in claim 14 wherein said plane of said
groove areas and said plane of said land areas are parallel.
16. A method as claimed in claim 11 which includes a series of
groove areas, some of which are positioned at an angle greater than
0 degrees to a machine direction.
17. A method as claimed in claim 16 wherein said series of groove
areas are in a cross hatched pattern.
18. A method as claimed in claim 11 wherein said perforations are
dispersed throughout both said land areas and said groove areas,
and wherein one or more of said perforations lies across the
interface of a land area and a groove area.
19. A method as claimed in claim 11 wherein said perforations are
only in said groove areas.
20. A method as claimed in claim 11 wherein said perforations are
only in said land areas.
21. A layer for use in a papermakers' fabric formed by creating a
plurality of grooves in a base material so as to form a modified
base material having a plurality of land areas and a plurality of
groove areas, and perforating said modified base material so as to
form a plurality of perforations extending from a top surface to a
bottom surface in said modified base material, wherein the
combination of said land areas, groove areas and perforations
minimize pattern formation on said paper sheet.
22. A layer as claimed in claim 21 wherein said groove areas lie in
a plane.
23. A layer as claimed in claim 21 wherein said land areas lie in a
plane.
24. A layer as claimed in claim 21 wherein said groove areas lie in
a plane and said land areas lie in a plane.
25. A layer as claimed in claim 24 wherein said plane of said
groove areas and said plane of said land areas are parallel.
26. A layer as claimed in claim 21 which includes a series of
groove areas, some of which are positioned at an angle greater than
0 degrees to a machine direction.
27. A layer as claimed in claim 26 wherein said series of groove
areas are in a cross hatched pattern.
28. A layer as claimed in claim 21 wherein said perforations are
dispersed throughout both said land areas and said groove areas,
and wherein one or more of said perforations lies across the
interface of a land area and a groove area.
29. A layer as claimed in claim 21 wherein said perforations are
only in said groove areas.
30. A layer as claimed in claim 21 wherein said perforations are
only in said land areas.
31. A press fabric claimed in claim 25 wherein said perforations
are only in said land areas.
32. A papermakers' press fabric, comprising a layer having: a
plurality of land areas oriented substantially in the machine
direction; a plurality of groove areas oriented substantially in
the machine direction; a plurality of perforations, extending from
a top surface to a bottom surface of said layer; and wherein the
combination of said land areas, groove areas and perforations
minimize pattern formation on said paper sheet.
33. A press fabric as claimed in claim 32 wherein said groove areas
lie in a plane.
34. A press fabric as claimed in claim 32 wherein said land areas
lie in a plane.
35. A press fabric as claimed in claim 32 wherein said groove areas
lie in a plane and said land areas lie in a plane.
36. A press fabric as claimed in claim 35 wherein said plane of
said groove areas and said plane of said land areas are
parallel.
37. A layer as claimed in claim 32 wherein said series of groove
areas are in a cross hatched pattern.
38. A press fabric as claimed in claim 32 wherein said perforations
are dispersed throughout both said land areas and said groove
areas, and wherein one or more of said perforations lies across the
interface of a land area and a groove area.
39. A press fabric claimed in claim 32 wherein said perforations
are only in said groove areas.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the papermaking arts. More
specifically, the present invention relates to press fabrics for
the press section of a paper machine.
2. Description of the Prior Art
The production of paper begins with the processing of wood. Wood is
chiefly composed of two major substances, cellulose and lignin;
both are organic, that is, their molecules are built around chains
and rings of carbon atoms. Cellulose occurs in the walls of the
plant cells and is the fibrous material that is used to make paper.
Lignin is a large complex molecule that acts as a kind of glue that
holds the cellulose fibers together and stiffens the cell walls,
giving wood its mechanical strength. In order to convert wood into
pulp suitable for making paper, the cellulose fibers must be freed
from the lignin.
During the papermaking process, a cellulosic fibrous web is formed
by depositing a fibrous slurry, that is, an aqueous dispersion of
the cellulose fibers, onto a moving forming fabric in the forming
section of a paper machine. A large amount of water is drained from
the slurry through the forming fabric, leaving the cellulosic
fibrous web on the surface of the forming fabric.
The newly formed cellulosic fibrous web proceeds from the forming
section to a press section, which includes a series of press nips.
The cellulosic fibrous web passes through the press nips supported
by a press fabric, or, as is often the case, between two such press
fabrics. In the press nips, the cellulosic fibrous web is subjected
to compressive forces which squeeze water therefrom, and which
adhere the cellulosic fibers in the web to one another to turn the
cellulosic fibrous web into a paper sheet. The water is accepted by
the press fabric or fabrics and, ideally, does not return to the
paper sheet.
The paper sheet finally proceeds to a dryer section, which includes
at least one series of rotatable dryer drums or cylinders, which
are internally heated by steam. The newly formed paper sheet is
directed in a serpentine path sequentially around each in the
series of drums by a dryer fabric, which holds the paper sheet
closely against the surfaces of the drums. The heated drums reduce
the water content of the paper sheet to a desirable level through
evaporation.
It should be appreciated that the forming, press and dryer fabrics
all take the form of endless loops on the paper machine and
function in the manner of conveyors. It should further be
appreciated that paper manufacture is a continuous process which
proceeds at considerable speeds. That is to say, the fibrous slurry
is continuously deposited onto the forming fabric in the forming
section, while a newly manufactured paper sheet is continuously
wound onto rolls after it exits from the dryer section.
The present invention relates specifically to the press fabrics
used in the press section. Press fabrics play a critical role
during the paper manufacturing process. One of their functions, as
implied above, is to support and to carry the paper product being
manufactured through the press nips.
Press fabrics also participate in the finishing of the surface of
the paper sheet. That is, press fabrics are designed to have smooth
surfaces and uniformly resilient structures, so that, in the course
of passing through the press nips, a smooth, mark-free surface is
imparted to the paper.
Perhaps most importantly, the press fabrics accept the large
quantities of water extracted from the wet paper in the press nip.
In order to perform this function, there literally must be space,
commonly referred to as void volume, within the press fabric for
the water to go, and the fabric must have adequate permeability to
water for its entire useful life. Finally, press fabrics must be
able to prevent the water accepted from the wet paper from
returning to and rewetting the paper upon exit from the press
nip.
Contemporary press fabrics are produced in a wide variety of styles
designed to meet the requirements of the paper machines on which
they are installed for the paper grades being manufactured.
Generally, they comprise a woven base fabric into which has been
needle-punched a batt of fine, non-woven fibrous material. The base
fabrics may be woven from monofilament, plied monofilament,
multifilament or plied multifilament yarns, and may be
single-layered, multi-layered or laminated. The yarns are typically
extruded from any one of several synthetic polymeric resins, such
as polyamide and polyester resins, used for this purpose by those
of ordinary skill in the paper machine clothing arts.
The woven base fabrics themselves take many different forms. For
example, they may be woven endless, or flat woven and subsequently
rendered into endless form with a woven seam. Alternatively, they
may be produced by a process commonly known as modified endless
weaving, wherein the widthwise edges of the base fabric are
provided with seaming loops using the machine-direction (MD) yarns
thereof. In this process, the MD yarns weave continuously back and
forth between the widthwise edges of the fabric, at each edge
turning back and forming a seaming loop. A base fabric produced in
this fashion is placed into endless form during installation on a
paper machine, and for this reason is referred to as an
on-machine-seamable fabric. To place such a fabric into endless
form, the two widthwise edges are brought together, the seaming
loops at the two edges are interdigitated with one another, and a
seaming pin or pintle is directed through the passage formed by the
interdigitated seaming loops.
Further, the press fabric may be formed of several layers. For
example, the fabric may include a woven base and an intermediate
layer that are laminated together. One such fabric is the Albany
International Apertech.TM. press fabric, which includes a woven
base fabric and a polymeric layer. The polymeric layer of the
Apertech.TM. fabric is perforated and is illustrated in FIG. 1.
FIG. 1 is a plan view of the paper side of the polymeric layer, in
which the polymeric layer is generally indicated by reference
numeral 1 and the perforations by reference numeral 4. As can be
seen from the figure, surface 1 is smooth and the perforations are
evenly distributed across the surface.
The present invention relates primarily to an improvement in a
perforated layer of a papermakers' fabric, such as the layer used
in the Apertech.TM. fabric.
SUMMARY OF THE INVENTION
The inventor of the present invention has recognized that in some
applications of a papermakers' fabric with a perforated layer, the
hole pattern of the perforated layer is replicated in the paper
sheet. The inventor has further recognized that such marking is
caused by collections of fines having a relatively high density of
lignin in the paper web. More specifically, hole pattern
replication in the paper is due to fluid flow concentrations
through the holes which cause migration of fines and their
associated lignin which give rise to light/dark contrasting areas
in the paper.
In view of the drawback caused in certain applications by the
perforated layer of a papermakers' fabric, it is an object of the
invention to diffuse flow at the surface of the perforated layer so
as to reduce the pressure drop across the layer and thereby reduce
flow concentration through the holes and hence the migration of
fines in the paper web. To realize this objective, a grooved
perforated layer is provided. The grooves serve to diffuse flow and
reduce the migration of fines so that the light/dark pattern
associated with the fines is avoided and the quality of the
resulting paper sheet is improved.
BRIEF DESCRIPTION OF THE DRAWINGS
The following detailed description, given by way of example and not
intended to limit the present invention solely thereto, will best
be appreciated in conjunction with the accompanying drawings,
wherein like reference numerals denote like elements and parts, in
which:
FIG. 1 is a plan view of a related art perforated layer of a
papermakers' fabric;
FIG. 2 is a plan view of a perforated layer according to one
embodiment of the invention;
FIG. 3 is a plan view of a perforated layer according to another
embodiment of the invention;
FIG. 4 is a plan view of a perforated layer according to still
another embodiment of the invention; and
FIG. 5 is a cross-sectional view of a perforated layer according to
the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A preferred embodiment of the present invention will be described
in the context of papermaking press fabrics. However, it should be
noted that the invention is applicable to fabrics used in other
sections of a paper machine, as well as to those used in other
industrial settings where diffusion of flow across a surface of a
fabric improves the fabric's performance.
Some examples of other fabric types to which the invention is
applicable include papermakers' forming fabrics, papermakers' dryer
fabrics, through-air-drying fabrics and pulp forming fabrics.
Another example of a fabric type to which the invention is
applicable is engineered fabrics, such as fabrics used in making
non-woven textiles in the wetlaid, drylaid, meltblown and/or spun
bonding processes.
FIG. 2 is a plan view of a section of a perforated layer in
accordance with the invention. As can be seen from FIG. 2, the
layer includes a multiple of land areas 10, a multiple of groove
areas 8 and a multiple of perforations 6. The groove areas lie in a
plane below the plane in which the land areas lie. A cross-section
of the layer is shown in FIG. 5.
Referring to FIG. 5, it can be seen that the plane of the groove
areas lies a distance "t" below top surface 24 of the layer. The
plane of the groove areas defines the groove depth. As can be seen,
the groove depth is equal to about one-quarter of the overall
thickness "T" of the layer--the overall thickness being defined as
the distance from the top surface, defining the plane of the lands,
to the bottom surface 26. For purposes of clarity of presentation,
only three perforations 28 are shown in FIG. 5.
It should be noted that the groove depth is not limited to being
about equal to one-quarter of the overall thickness, but may be
varied according to the material(s) used to form the layer and the
desired properties of the finished layer. It is also noted that,
although the grooves have been described as having uniform depth,
an alternative embodiment includes grooves of varying depth, in
which case the groove areas would not all lie in a single plane
parallel to a surface plane. That is, in the alternative
embodiment, the groove areas do not lie in a plane, or lie in a
plane that is not parallel to either the top surface plane or
bottom surface plane. Furthermore, it is possible to vary the
height of the land areas such that the top surface of the layer has
an uneven construction and the land areas no longer lie in a single
plane. Still further, it is noted that in the FIG. 2 embodiment,
some perforations lie partly in a groove and partly in a land. It
is possible to form the layer such that each perforation lies
either entirely in a groove or entirely in a land, with no
perforation lying across a land/groove interface. In any event, the
perforations may be formed either before or after grooves are
formed.
It is also conceivable that the grooves can be at an angle with the
machine direction. Furthermore, there can be two series of grooves
at an angle to each other in a cross hatch pattern.
FIG. 3 is a plan view of a section of a perforated layer in
accordance with another embodiment of the invention. As can be seen
from FIG. 3, all perforations 12 are confined to groove areas 14
and no perforation lies in any land area 16. In the FIG. 3
embodiment, all of the variations discussed in connection with the
FIG. 2 embodiment are applicable, with the exception of the
variations regarding placement of the perforations.
FIG. 4 is a plan view of a section of a perforated layer in
accordance with still another embodiment of the invention. As can
be seen from FIG. 4, all perforations 18 are confined to land areas
22 and no perforation lies in any groove area 20. All of the
variations discussed in connection with the FIG. 2 embodiment are
applicable to the FIG. 4 embodiment, with the exception of the
variations regarding placement of the perforations.
Regardless of embodiment, it is preferable to combine the grooved
and perforated layer of the invention with other layers in order to
realize a papermakers' press fabric. For example, the grooved and
perforated layer of the invention may be substituted for the
perforated layer of the Apertech.TM. fabric to thereby construct a
"grooved Apertech.TM.."
In any embodiment, the invention diffuses flow at the surface of a
perforated layer of a papermakers' fabric. The diffusion of flow
reduces the pressure drop across the layer and thereby reduces the
migration of fines which has the effect of reducing/avoiding the
light/dark pattern that such migration imparts to the paper
sheet.
Modifications to the present invention would be obvious to those of
ordinary skill in the art in view of this disclosure, but would not
bring the invention so modified beyond the scope of the appended
claims.
* * * * *